My invention relates to a method and machinery for the production of pulp and for postrefining of such pulp from fibrous ligno-cellulose raw materials for the production of paper, paperboard, fiberboard, formed products for shipping containers, dry formed board and many other useful products. The invention can also in certain cases be used for dispersion and pulverizing of ceramics and other products, which for its further manufacture has to be kneaded or mixed with other additives. The material under processing will in the following be called "grist". The invention comprises a process where the material is compressed and accelerated within a closed, or nearly closed, cylinder, hereinafter called the "drum" by a rotary member concentric with the cylinder and equipped with blades, hereinafter called "impellers", compressing by centrifugal force the grist in a radial direction against the walls of the drum and the refining members, hereinafter called "staves" located on the inside wall of the cylinder or drum. The staves are equipped with edges perpendicular to the path of the accelerated grist, which moves between the rotating impellers and the stationary edges, thus creating within the grist planes of frictional shear forces.
According to the U.S. Pat. No. 3,547,536 granted the applicant a similar method is disclosed where the inside wall of the cylinder in the axial direction is equipped with grooves of limited radial extent where small quantities of the grist is retarded whereas at the same time the impellers keep the main part of the grist in rapid rotation. The layers of grist moved by the impellers and the layers of grist retarded by the grooves on the inside of the cylinder are refined along the plane of shear created between the two layers of grist. The obstructions formed by the grooves according to the known method are sequentially arranged with gradual slopes in order that the refining action shall be accomplished mainly through the internal friction created between the fibers themselves when they pass through the concentric slot between the impellers and the undulations on the inner wall of the cylinder.